POCT Quality Assurance (QA)
Quality Assurance is a vast subject and is of fundamental importance to every laboratory department. It could be argued that QA involvement in POCT is of even greater significance, since laboratory testing is being performed by non-laboratory professionals whose training in quality issues may have been less rigorous than that given to laboratory professionals. This argument presents a strong case for mandatory competency.
Quality Assurance is an overview and examination of a complete system, from approaching the patient with the intention of obtaining a sample to looking at the subsequent result report from the laboratory or POCT analyser.
Large parts of Quality Assurance involve Quality Control (QC), Proficiency Testing and External Quality Assessment (EQA). Without successful QC results, correct patient results cannot be assumed.
Although not covered in the table below, attention must be given to:
- analyser maintenance schedules
- hardware and software replacements and upgrades
- service records
- annual preventative maintenance reports
- complete documentation records
- quality control records
A good approach is to divide the QA process into three phases, Pre-Analytical, Analytical and Post-Analytical:
All staff who operate POCT equipment should have an awareness of and be responsible for:
- identifying the patient correctly
- the quality of the patient's sample to be analysed
- ensuring the analyser or procedure is calibrated correctly
- analysing any required Quality Control (QC) samples
- regular analyser or procedure maintenance
- documentation of all QC results, patient results, maintenance records, troubleshooting records, error messages
- their current competency requirements for all relevant POCT processes
To confirm the ID of a patient, two points of ID must be cited. The acceptable choices are in descending order of importance: NHI number, e.g., XYZ9876; hospital temporary allocated number; surname and given name; date of birth.
Regardless of whether the puncture site be a heel, digit, ear lobe or elbow, it is important for the sake of a good sample that the puncture site be:
-
clean
-
dry
-
healthy
-
not the drip arm
-
free from contaminants, e.g., saliva, sugar (from sweets, drinks, etc)
-
alcohol free (from sterilizing swabs)
Other types of samples, like cerebrospinal fluid (CSF), urine, stool, drain fluids, wound swabs, skin scrapings, etc must also be collected carefully, in an aseptic manner. The quality of the sample determines the quality of the results.
-
Always wash your hands before approaching the patient
-
Wear gloves (and wash your hands between patients, even if wearing gloves).
-
Wear prescribed protective clothing if dealing with infectious patients.
-
Prepare the puncture site or sample site as described above.
-
Always wash your hands after leaving the patient.
Most POCT samples are arterial (blood gases) or capillary blood in nature.
Phlebotomy staff collect most venous patient samples by venepuncture; however, it is important for all staff to know which collection tubes are appropriate for which blood test.
The order of draw is very important.
From first to last, in sequence: blood cultures, red top, SST, blue, green, lavender, grey. The reason for this sequence is to minimise tube contamination from additives and anticoagulants. Sterilise the entry point of the blood culture tubes before inoculating them.
These colour codes relate to Becton-Dickinson brand products, whether for macro-collecting (venepuncture) or micro-collecting (capillary) samples:
| Blood culture tubes | Blood cultures |
|
Red top (Plain tube- no additives) SST(serum separator tube) |
Some Biochemistry, Serology, Virology, crossmatching . |
| Dark blue (chemically clean) | Trace Metal tests |
| Light blue top (citrate) | Haemostasis tests |
|
Green top (Lithium heparin) |
Routine Biochemistry tests |
| Lavendar or purple top (EDTA) | Haematology; blood lead testing, crossmatching |
| Gray top (fluoride) | Glucose, lactate. |
Capillary blood gases need to be collected into special balanced-heparin blood gas capillary collection tubes. Click here for more information on capillary blood collecting.
Always make sure your sample is WELL MIXED. Try not to expose a blood gas capillary sample to ambient air as gas partial pressures in the sample may change. Mix your capillary blood gas sample by holding the tube horizontally and rolling it back and forth between finger and thumb. Don't slosh it back and forth along the tube. Do not use pO2 readings- capillary blood collects are exposed to too much ambient oxygen. In addition, peripheral perfusion is too variable for consistent pO2 readings.
All collection tubes and request forms must be labelled clearly with the patient's ID sticker and barcode. When this is not available, their National Heath Institute (NHI) number or temporary hospital number, surname and date of birth must be written on the tube(s). The request form must state clearly which tests are required and include the same patient information as the sample collection tubes. The request form should also include the date and time of sample collection as well as a clear indication of the requesting doctor and location of the patient.
A long delay can occur when samples sent to the laboratory for analysis are delivered tardily. This may be for a variety of reasons- a delay in pickup from the ward or delivery forgotten en route to the lab. A delay of several hours may result in lowered blood glucose, raised potassium, phosphate and CK- all a result of cellular metabolism or perhaps, haemolysis. The life span of a blood gas is limited to 60 minutes at room temperature.
Many hospitals now utilise a pneumatic tube delivery system which solves the transport delay times. However, tube breakdowns can occur, for a variety of reasons, human, electronic or mechanical.
POCT obviates any need for sample transport to the laboratory.
ANALYTICAL TECHNIQUE
Analyser operation; operator and patient ID entry
The relevant operator's manual will contain instructions for analyser operation. All clinical staff operating POCT analysers should have a current competency which includes instructions on how to operate POCT equipment.
All POCT actions and results must be able to be traced or audited. This means that print outs, transcriptions, electronic results must contain the POCT operator's ID (or initials at the very least) and the patient's ID. The date and time of analysis and sample type must also be noted on the results.
Venous sample: After collecting your venous sample, gently invert and roll the collection tubes at least five times, to thoroughly mix the anticoagulant in the tube with the blood.
Arterial blood gas sample: at the blood gas analyser, mix the arterial or capillary blood gas sample by holding the tube horizontally and rotating it between fingers and thumb. (Do not overheat the syringe through friction of palms while mixing, as gas pressures will drop due to temperature increase). Alternate this action with gentle inversions of the syringe. There must be no air bubbles present in the syringe or capillary sample.
Capillary blood gas tubes: try not to slosh the blood back and forth along the length of the capillary tube. Rotate by rolling the tube horizontally between your fingers. Keep the blood/air contact to a minimum. Remove caps and any metal flea or mixer before aspirating the sample.
If you are analysing an arterial blood gas sample for CO-Oximetry:
i.e., (haemoglobins and oxygen saturation parameters), it is vitally important that the sample be well-mixed. Gently rotate and invert the blood gas syringe for at least 30 seconds before aspirating the sample. The blood must be as homogenous as if it were still in the patient. (The reason for this is in the method of analysis of the haemoglobins- a sample of blood is electronically haemolysed and the intensity of the clear red solution of blood is measured at certain wavelengths).
Always follow the manufacturer's guidelines on sample analysis. Clear simple instructions should be posted near the analyser. Failure to analyse the sample properly will lead to erroneous quality control and patient results.
Where an analyser is in use, correct maintenance schedules must be maintained. Always fulfil any daily maintenance criteria required and sign and date the maintenance logs. Note any consumable replacements, e.g., reagents or calibrators and also make note of any changes in lot numbers. Any change in the status quo of the analyser, like reagent changes, cartridge or test strip lot number changes, etc, MUST be followed by a successful calibration and after that, a successful quality control sample result; only after the QC has passed successfully, may patient samples be analysed.
All analytical procedures, whether POCT or laboratory-based in nature must be calibrated before use. Calibrating a procedure means that you are measuring a starting point from which all other measurements depend. A quality control (QC) sample tests the correctness of the calibration. Many people confuse these two concepts. Click on this link for an in depth discussion of calibration vs. quality control.
Most blood gas analysers self-calibrate every 30 minutes or so. If analyser conditions have not altered between timed calibrations, no QC is necessary. For conditions when QC is or is not required after a calibration, please refer to the link in the previous paragraph.
Abbott i-STAT analysers calibrate themselves immediately before patient sample analysis- the blood sample is placed into the reservoir on the cartridge, the cartridge is sealed and inserted into the analyser. Calibration occurs- a small on-board sac is ruptured, the calibration fluid moves across the electrodes, measurement is taken and then the patient sample is analysed. Energies are compared, calculations made and results are then available. Where this type of single-use cartridge is concerned, the manufacturer's recommendation is to take two cartridges at random from each new box and test them for QC. After that, your faith must rest with the manufacturer's production quality control. Of course, any discrepant results must be confirmed by re-testing or by sending a sample to the laboratory.
Manual POCT that does not involve analysers may not need to be calibrated: a visually interpreted urine test strip is an example of this. Wherever possible though, a quality control sample should always be analysed daily before patient testing begins, or if the conditions of analysis are changed in any way.
Quality Control (QC) samples and patient samples should be analysed using identical techniques and under identical conditions. The only difference is that the value(s) of the QC samples are known, whereas the patient 's values are not. If the correct QC results are obtained, we can say with confidence that the last calibration was successful, the analyser or process is functioning correctly, the operator's skills are sufficient and that the patient's results will therefore be correct.
If you have not analysed a QC sample and obtained acceptable results, you cannot assume that the patient results will be correct.
Each POCT analyser is accompanied by a Users' Manual, compiled by the POCT Coordinator. Within this Manual will be a rudimentary section on troubleshooting. Often a problem that seems insurmountable can be easily resolved by restarting the analyser*- turn it off, wait 10 seconds and turn it on again. On the other hand, a blood clot can be tricky to remove from a blood gas analyser.
*Not recommended for blood gas analysers which may take some time to return to normal running conditions after a reboot.
An Error Log can be found in each Manual. Please take the time to document any problems that occur. This is important, as a documented history of problems can be very useful for warranty or replacement purposes. It is also an ISO22870 Accreditation requirement that all errors be documented and that a complete audit trail exists for each entry, including resolution of the error or problem.
If you have a problem that you cannot resolve or you have insufficient time to repair the problem, please contact the POCT Coordinator who is there to be used as a resource and a source of assistance.
Consumable and reagent quality
Reagents, cartridges and other consumables must not be used after their expiry date and be discarded.
Lot numbers of reagents, cartridges and other consumables will change occasionally. A calibration must occur after any changes are made to the system, even if lots numbers are identical.
A QC analysis must be made after any calibration. The QC must be correct before any patient samples are analysed.
All consumable changes and lot numbers must be documented on the appropriate Consumables Worksheet for the test in question (see the Appendix of the Operator's Manual for documentation and mastercopies).
Maintenance and troubleshooting records
All maintenance and troubleshooting logs are retained and kept for an extended period of time. These logs list reagents and consumables used, QC results, problems solved and parts replaced. Each day's maintenance is signed off by the laboratory personnel or accredited representative involved.
More information is available on the Quality Assurance page.
For any additional advice, assistance, lectures, troubleshooting issues or meter replacements, please contact the POCT Coordinator.
Post-Analytical Technique
Correct sample disposal; cleanliness and tidiness
All samples must be discarded into Medical Waste containers. Any body fluid-contaminated tissues or other waste must also be discarded into Medical Waste containers.
DO NOT throw any body fluid-contaminated waste into regular paper waste containers.
All sharps- needles and so forth must be discarded into a Sharps Container.
Always clean up any spills- use Precept disinfectant or 5% bleach- to ensure the analyser and surrounds are maintained in a clean and tidy condition. Always leave the POCT analyser or place of work in the same condition as you would expect to find it.
Examination, interpretation, notification , inclusion.
-
All POCT operators should have an awareness of the meaning of the results they generate. The results should be examined with respect to units of measurement, reference intervals, meaning of abnormal results, implication to the patient and so on.
-
Abnormal whole blood results that are not expected or do not fit with the clinical picture of the patient should be confirmed before being reported. Use a new sample- it is possible that the initial sample is contaminated in some way- tissue fluid, drip arm, clots, etc. If the result is still abnormal, send a venous sample to the laboratory for plasma analysis. (There are several shortcomings to whole blood analysis).
-
Document ANY ERROR CODES that may be generated; note how the results may be affected. Contact the POCT Coordinator for advice, if required.
-
Any abnormal results should be referred to the patient's physician or senior ward/clinic staff for action and advice.
-
All results should be recorded in, transcribed or affixed to the patient's notes, along with the operator ID , and the time and date of analysis.
All POCT results must be of the same standard as laboratory results. This statement lies at the heart of successful POCT. One of the requirements of laboratory testing is the successful passing of audits. All POCT results must be able to pass an audit. This means that the results must be able to be traced to:
-
the patient
-
the operator
-
the machine or process used
-
relevant maintenance and QC logs
-
the date and time
-
current competency records held by the operator
External Quality Assessment and Proficiency Testing
All POCT must be quality controlled (QC) regularly. While QC is generally regarded as a day-to-day procedure for each analyser or procedure, External QA is performed at less regular intervals, typically monthly. CHLabs belongs to the RCPA-QAP (Royal College of Australasian Pathologists- Quality Assessment Program).
Proficiency Testing or sample correlation testing is another approach to QC. Proficiency testing can involve more than a single laboratory or POCT site. Click on Proficiency Testing for more information.
